It is known to use electrical power steering, commonly abbreviated as EPAS, in a vehicle such as a car, lorry, bus or truck, wherein an electric motor assists a driver of the vehicle by adding an assistive torque to e.g., a steering column. It is further known to use a lane keeping aid system in order to help the driver keep in the lane. For lane keeping aid systems where the EPAS is used, a steering wheel torque overlay, i.e., additional steering wheel torque on top of what would have been obtained by the base assist of the EPAS, is used for lateral position control. The present disclosure relates to an adaptation of such a steering wheel torque overlay. However, the principles of the present disclosure are independent of the EPAS and may also be used in a vehicle without EPAS for adapting the steering wheel torque overlay.
Document US 2010/0004821 A1 discloses a device for keeping a vehicle in its lane, including a reference model, which obtains geometric data regarding the position of the vehicle in the lane as well as data relating to the course of the lane from a lane detection system, and from these calculates a set point variable for controlling the vehicle position. In order to allow for corners to be cut, the guiding behaviour of the control system is modified in such a way when cornering that, in the event of a deviation of the path of motion of the vehicle from the set point path of motion in the direction of the inside of the road curve, no or only low steering forces are applied to the steering system. In an embodiment, illustrated in FIG. 3b of US 2010/0004821 A1, a characteristic controller curve is widened asymmetrically while the driver cuts a corner and a dead zone is created, wherein no guide torque is produced in spite of a system deviation. It is further stated that the control characteristic curve may have a P-behaviour and in particular not an I-behaviour.
The system disclosed in US 2010/0004821 A1 discloses a static regulator for the angle deviation, wherein the characteristic curve is influenced by different variables of the vehicle and environment. When cutting a road curve, the reference value of the regulator is displaced while maintaining the general shape of the characteristic curve. Moreover, US 2010/0004821 A1, relates to driving in road curves. Driving straight ahead is not mentioned.